1. Field of the Invention
The present invention relates generally to a defect-position identifying method for a semiconductor substrate.
2. Description of the Related Art
With the high density integration of ULSIs, zero defects in the surface layer of a semiconductor substrate serving as an element active layer are required. It is generally known that defects due to pull-up, called on grown-in defects, exist in the crystal of a semiconductor substrate which is obtained by slicing and polishing a single crystalline silicon pulled up from a crucible. These defects have only a density of about 10.sup.6 cm.sup.-' detected mainly by light scattering. Therefore, it is very difficult to carry out the direct observation by means of a transmission electron microscope (which will be also hereinafter referred to as a "TEM") or an atomic force microscope (which will be also hereinafter referred to as an "AFM"), and the substance thereof did not clear until recent years.
However, it was succeeded in 1995 to observe defects themselves in a gate oxide film by means of a TEM by utilizing the copper's property of being selectively deposited on defect existing places, and it was revealed that most of these defects comprised voids.
In general, systems for evaluating a semiconductor substrate having defects are classified into two kinds of systems, i.e., systems for macroscopically catching the presence of defects, and systems for microscopically catching the presence of defects. The macroscopically catching systems are classified into two kinds of systems, i.e., systems for catching defects on the surface of a semiconductor substrate (e.g., a particle counter), and systems for catching defects directly below the surface of a semiconductor substrate (e.g., a visible light scattering topography), as shown in FIG. 16. The microscopically catching systems are classified into two kinds of systems, i.e., systems for catching defects on the surface of a semiconductor substrate (e.g., AFM), and systems for capturing defects directly below the surface of a semiconductor substrate (e.g., a scanning capacitance microscope (which will be also hereinafter referred to as a "SCM") and a cross-section TEM), as shown in FIG. 16. Furthermore, although the SCM originally carries out an evaluating method for obtaining a two-dimensional distribution of the density of dopant (impurity) in a semiconductor element, the SCM can also be used for evaluating defects below the surface, which can not be observed by the AFM.
In order to identify the position of a defect, it is general to evaluate the defect by a microscopically catching system after evaluating the defect by a macroscopically catching system. It is therefore important to deliver coordinate values indicative of the position of the defect between the macroscopically catching system and the microscopically catching system.
Conventionally, the coordinate values of the defect have been measured by using the X-Y stage of each of systems, on which a semiconductor substrate is mounted, and the shape of the semiconductor substrate (a circumference and an orientation flat or notch).
However, there is a limit to the mechanical precision of the stage, and the shape of the semiconductor substrate has errors during working. Therefore, even if a defect is found by the macroscopically capturing system, the defect does not always come within the range of the microscopically catching system, so that there is a problem in that the position of the defect can not be identified.